Question: Tiffany is 74 years old and Stephanie is 20 years old. How many years will it take until Tiffany is only 3 times as old as Stephanie?
Explanation: We can use the given information to write down an equation about how many years it will take. Let $y$ be the number of years that it will take. In $y$ years, Tiffany will be $74 + y$ years old and Stephanie will be $20 + y$ years old. At that time, Tiffany will be 3 times as old as Stephanie. Writing this information as an equation, we get: $74 + y = 3 (20 + y)$ Simplifying the right side of this equation, we get: $74 + y = 60 + 3 y$ Solving for $y$ , we get: $2 y = 14$ $y = 7$.